Sol-gel synthesis of Ag-doped titania-coated carbon nanotubes and study their biomedical applications

In this paper, we report the formation of new conjugates constituting single-wall nanotube (SWNTs) and multi-wall nanotube (MWNTs) comprising silver-doped titanium dioxide (TiO2/Ag) having outstanding antimicrobial and toxic properties. At first, the raw SWNTs and raw MWNTs were chemically treated with sulfuric acid and nitric acid to produce functionalized SWNTs (F-SWNTs) and functionalized MWNTs (F-MWNTs) surface. Then TiO2/Ag nanoparticles (NPs) were loaded with F-SWNTs and F-MWNTs using in situ sol-gel technique. The raw SWNTs, raw MWNTs, and conjugates' samples were characterized via ultraviolet-visible (UV-Vis) spectrophotometer, Fourier transform infrared (FTIR), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). These measurements confirmed the loading of TiO2/Ag NPs on SWNTs and MWNTs walls. The optical band gap of R-SWNTs and R-MWNTs was decreased from 3.74 to 3.6 eV and from 3.9 to 3.64 eV, respectively, after decoration of TiO2/Ag. The XRD results confirmed the hexagonal structure of R-SWNTs and R-MWNTs with (002) plane, while the conjugates' samples showed anatase phase of TiO2 with (101) plane. The R-SWNTs and R-MWNTs dispersions revealed poor killing ability toward both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In contrast, the prepared SWNTs-TiO2/Ag and MWNTs-TiO2/Ag conjugates exhibited significant inhibitory effect against bacterial strains after 24 h of incubation. The cytotoxicity of these newly developed conjugates was assessed toward uterine cancer (SiHa) cell and normal (WRL68) cell lines. The SWNTs-TiO2/Ag and MWNTs-TiO2/Ag conjugates were able to selectively kill tumor cells (similar to 60 to 40%), whereas less affecting normal cells (similar to 10%).